Not even a first-half penalty miss from Eric Maxim Choupo-Moting could stop the Royal Blues as they extended their unbeaten record to 12 matches in all competitions, including seven in the Bundesliga. After they lost their first five Bundesliga games of the season, Schalke's run has taken them up to eighth place with 17 points from 12 games.
Darmstadt, a lowly 15th, stunned the hosts when they took a sixth-minute lead from a move which started with a Schalke corner.
Sandro Sirigu collected the ball and burst down the right, then slipped the ball to Marcel Heller who rounded Ralf Faehrmann to score.
Sead Kolasinac equalised in the 26th minute, heading in from Choupo-Moting's cross.
The Cameroon forward had a chance to get on the scoresheet himself two minutes later when Schalke were awarded a penalty but Darmstadt goalkeeper Michael Esser saved the shot with his legs.
Choupo-Moting was not to be denied, however, and put Schalke ahead on the hour, poking home the ball from Max Meyer's cross.
Alessandro Schoepf sealed Schalke's win with a third goal in the final minute.